Pd/Brønsted Acid-Catalyzed Atom-Economical [3 + 3] Annulation of 4-Hydroxycoumarins and Skipped Enynes
Bhavya Khaitan1, Shikha Gandhi1
1Department of Chemical Sciences, Indian Institute of Science Education and Research Berhampur, Berhampur, Odisha 760010, India.
Abstract:
We report an unprecedented application of skipped enynes as bis-electrophiles under palladium/Brønsted acid catalysis. A [3 + 3] annulation of skipped enynes with 4-hydroxy coumarins as bis-nucleophiles enables a completely atom-economic synthesis of fused O-heterocycles. The reaction is proposed to proceed via the Pd-catalyzed C-H activation of the skipped enyne leading to a diene, which upon subsequent activation by Pd and an O-nucleophilic attack leads to the regioselective formation of a six-membered heterocyclic ring, with a vinyl substituent.
Related Concept Videos
Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
Dehydration of Aldols to Enones: Acid-Catalyzed Aldol Condensation
Synthesis of α-Substituted Carbonyl Compounds: The Stork Enamine Reaction
Radical Anti-Markovnikov Addition to Alkenes: Overview
α-Bromination of Carboxylic Acids: Hell–Volhard–Zelinski Reaction
Radical Anti-Markovnikov Addition to Alkenes: Mechanism
The mechanism starts with chain initiation, which involves two steps. In the first chain initiation step, a weak peroxide bond is homolytically cleaved upon mild heating to form two alkoxy radicals. In the second initiation step, a hydrogen atom is abstracted by the alkoxy...


